Electrophotographic imaging devices, such as laser printers, fax machines, and photocopiers, are designed to produce a desired image on a print media, such as a sheet of copy paper. Electrostatic imaging devices generally include a photoconductive element that is selectively discharge by illumination from a scanned laser beam or light emitting diode array in response to data representative of the desired image that is to be produced, wherein the incident light generates a latent electrostatic copy of the desired image on the photoconductive element. The latent electrostatic copy is then developed by first exposing the photoconductive element to toner powder that adheres to the discharged portions of the photoconductive element and subsequently transferring the toner powder from the photoconductive element to the print media. The “loose” toner powder is then fused to the print media by a fuser unit.
Fuser units typically employ a combination of heat and pressure to fuse the toner powder to the print media. A fusing unit may employ a pair of opposing rollers that form a fusing nip, with one roller serving as a fuser roller and the other roller serving as a pressure roller. The fuser roller generally contacts the un-fused toner, while the pressure roller applies a pressure, or nip force, at the fusing nip to hold the print media in contact with the fuser roller. The fuser roller is generally heated while the pressure roller may or may not be heated. To fuse the looser toner to the print media, a fuser motor rotates the fuser and pressure rollers in a forward direction causing the print media to be drawn through the fusing nip, at which point the combination of pressure and heat from the rollers melts the loose toner and permanently affixes it to the print media.
In order to properly fuse the loose toner to the print media, fuser units are generally maintained at temperatures between 150° C. and 200° C. and may store a large amount of heat energy even after the associated imaging device is powered-off. In some instances, the amount of stored heat energy may be so large that the fuser unit may remain at high temperatures for several tens of minutes and potentially damage imaging system components if not properly dissipated. For instance, if the platen rollers are not properly cooled, waste toner powder may potentially fuse to the roller surfaces or other imaging system components, or rising temperatures may damage photoconductors or partially fuse toner reservoirs, causing them to become sources of potential print defects.